Non-invasive physiological sensing devices are used to elicit physiological information about a patient's body to help doctors diagnose, monitor, and treat medical conditions. Certain of such devices, including oximeters that measure the oxygen content in biological tissue, use well-known near-infrared spectroscopy (NIRS) techniques. Such devices commonly include a control/display unit and a sensor, where the sensor is connected to the control/display unit through a flexible cable. The sensor typically comprises a single-piece opaque planar pad that houses one or more light sources (e.g., light emitting diodes) for transmitting light into a patient's body and one or more optical receivers for receiving the light reflected from the patient's body. The sensor further includes electronic components, typically in the form of a printed circuit board, that communicate with and control the operation of the light sources and the optical receivers. The sensor generally has a pressure sensitive adhesive directly on the surface of the pad where the light sources and optical receivers are exposed so that the sensor can be affixed to the patient's body.
Known sensor pads typically are made from or include a layer of hydrophobic material, which makes the sensor pad occlusive (i.e., prevents or limits the passage of moisture vapor). The occlusive nature of the pad prevents the normal transport of moisture from the surface of the patient's skin, thereby preventing such moisture from passing through the sensor pad and into the sensor electronics. While it is important to protect the sensor electronics from moisture, the occlusive nature of the sensor pad can also lead to skin irritation and bacteria growth resulting from the build-up of moisture on the surface of the patient's skin under the sensor pad. This is a particular concern in neonates, where the initial cells die and exfoliate during a short duration to create new skin.
To prevent the build-up of moisture between a sensor pad and the patient's skin, it is a common practice for medical personnel to periodically remove the sensor from the patient's skin so that the area under the sensor can “breathe.” But the sensors are typically configured to be one-time use devices and the repeated removal and replacement of the sensor tends to compromise the adhesive's ability to securely affix the sensor to the patient's body, which can degrade the quality of the data obtained by the sensor. Accordingly, in practice, medical personnel tend to dispose of the old sensor and replace it with a new sensor each time they remove it from the patient's body. However, this practice can be very costly and thus undesirable. Therefore, there is a need for a sensor usable with an NIRS sensing system that is readily reusable and that facilitates the evaporation of moisture from the surface of the patient's skin while still protecting the sensor electronics from moisture damage.